Well, as Ms Hossenfelder could have learned at Twitter where she has debated these issues with real particle physicists, her remarks are controversial, to say the least. It's much less controversial to say that she doesn't have a clue what she is talking about. Let me elaborate on this statement in some detail.

High energy physics was a new name given to particle (or subnuclear) physics because the plan has been from the beginning to indefinitely raise the collision energy – and therefore the ability of the experiments to probe ever shorter distances (short distances are tied to high momenta/energies by the uncertainty principle). The rate of progress may slow down but it has always been clear that the progress could continue basically indefinitely.

In the first part of her new text, she makes it clear that she was looking for some "allies" who have questioned the future of particle accelerators just like she does. So she found a 2001 text in Physics Today by Maury Tigner, Does Accelerator-Based Particle Physics Have a Future?

Now, Tigner had been a big "design group" boss of the cancelled collider in Texas, the SSC. So what do you think was his answer to the question in his own article? Pretend that your IQ is above 70 if it is not and try to answer this question: Was Tigner, a collider boss, an anti-collider activist similar to Ms Hossenfelder?

Just to be sure, because there may be readers with the IQ below 70, I have to give a short answer to this "difficult" question: No, he wasn't.

In the very first paragraph, Ms Hossenfelder makes an extraordinary statement:

That the costs of larger particle colliders would at some point become economically prohibitive has been known for a long time. Even particle physicists could predict this.

As I have said, this statement is completely ludicrous. No physicist – and no person with the technical thinking at least at the high school level – has ever stated that "larger particle colliders would become economically prohibitive" at some point of time. The economy is generally growing, the technologies are generally improving, so of course that we may keep on building ever stronger particle colliders and that has always been the plan – that's why the field is called "high energy physics".

Maybe Sabine Hossenfelder, John Horgan, Uncle Al, and a bunch of similar "physicists" were saying something else to each other but actual physicists haven't. Of course there is no "end of physics".

She may have misunderstood the statement that some collision energy chosen on the log scale in between the LHC and Planck scale would be impossible to realize on Earth. Some energies such as \(10^{10}\GeV\) could be economically prohibitive and almost impossible on Earth. There's some order-of-magnitude estimate of the collision energy where we can't realistically get on Earth. But if you translate this "cutoff" to the moment of time or the year when particle physics should "hit the wall", you will surely not get a moment in the next 100 or 1,000 years. There is no reason for high energy physics to stop in the next millennium.

Even at the sociological level, such an "end of experimental particle physics" is as silly as the "end of sports" or "end of Olympic Games" or "end of Formula One" or "end of Miss USA" (OK, the latter has mostly occurred when the exhibitions in bikinis were replaced with contestants' left-wing political monologues). Athletes' performance is improving at a slower rate than it did in the past but it doesn't mean that we must abolish sports, does it? What's the fudging difference? Even if the rate of improvements slowed down incredibly, it would make sense to build new colliders. Although sports have been pointless for a long time, or always, some people still do similar stupid things. ;-)

And other, smarter people want to do particle physics. You can dislike baseball (I don't even like it enough to hate it LOL) but you won't prevent other people from playing or watching it. Similarly, Ms Hossenfelder may dislike particle physics but she's just a petty woman who makes Germany suck again and who can't prevent others, especially people from different nations and in a few years, from doing experimental particle physics.

Hasn't Maury Tigner, Hossenfelder's "source number one", written his own 2001 reaction to her 2019 statement about the "end of particle physicists at some point" that is "well known" and "predicted even by particle physicists"? Well, he has. This paragraph was fully focused on that claim:

The falloff in the energy frontier’s rate of advance might inspire the reader to ask whether we are approaching some inherent physical limit to the capability of accelerators, or perhaps some other limit. The answer is complex, but one thing is clear: We are not approaching a technical limit to the energies that can be achieved in the laboratory.

I added the bold face because Tigner, like any competent particle physicist, knows that there is no nearby limit. Larger tunnels and/or stronger magnets translate to higher energy collisions and the current colliders are extremely far from a limit, at least in the length of the tunnels – let's say that Earth radius could be such a limit, assuming that people won't build the colliders in outer space which they should.

Instead, Tigner – who clearly felt some responsibility for their failure to convince the U.S. Congress (and suggested that he would have been capable of "selling" a $1 billion experiment) – offers a detailed discussion about the rate of various prices. Some parts of the gadgets were getting cheaper extremely quickly, e.g. the superconducting wires, others were not. But let me post the Livingston Plot again:

Hossenfelder seems to use this plot as some kind of an argument in favor of her and Horgan's "end of science" delusions and she even wrote:

You can clearly see that the golden years of particle accelerators ended around 1990.

But only people with a severe enough eye disorder or with a brain disease may "clearly see" such a non-existent thing in the plot. Others see that the golden years are always in the future because the collision energy keeps on increasing. What she probably wanted to say is that the rate at which the collision energy was increasing per decade decreased after 1990 or so. But does it mean that "golden years of particle accelerators ended in 1990"?

This statement is exactly as true – or as false – as the statement

The golden years of the European and U.S. economy ended at the end of the 19th century.

Why? Because the average annual GDP growth was around 10% a year in the final decades of the 19th century. And we only expect some 3% today. Does it mean that the golden years of the economy stopped over a century ago? Well, if you define "golden years" as those with the highest annual growth, then yes. But no sane people do. The economy continued to grow after 1900 which is why it's just plain silly to say that the golden years of the economy occurred before 1900.

(By the way, we can debate what is behind the "disappointing" slowdown after 1900 or so. The low-hanging fruits of industrialization had been picked by 1900 or so – but I still think that the overregulation and overtaxation of the 20th and 21st century was more harmful. But I digress.)

It is even much more silly to say that the economy should have stopped producing things in 1900. And this is the actual perfect analogy of Hossenfelder's plan to give up on particle colliders. It's utterly uncontroversial that she has no idea what she is talking about.

The decadal rate of the increasing accelerator energy dropped around 1990 but the energy kept on rising and indeed, you can see that the Livingston Plot also includes a projection to the future colliders where the energy keeps on growing. The collision energy jumped by one order of magnitude each 10 years before 1990 – and the time needed for the 10-fold increase is closer to 20-30 years after 1990 (and it may be 200 years around 2300 AD). It's totally analogous to the slowed down GDP growth from 10% in the 19th century to 3% today.

But the GDP and the collision energy has no reason to stop growing.

In the following ten paragraphs, she repeats the mostly untrue statement that "colliders are damn expensive" several times while she adds some irrelevant details that have nothing to do with her basic wrong claims. At some moment, she gets to a comparison to LIGO:

Compare the expenses for CERN’s FCC plans to that of the gravitational wave interferometer LIGO. LIGO’s price tag was well below a billion US$. Still, in 1991, physicists hotly debated whether it was worth the money.

I love LIGO, I have rediscovered my gravitational waves from the raw LIGO data as well, and did lots of analyses, recommended the Nobel prize for the exact 3 men who really got it later, and so on. But it was still sensible to debate whether the gadget was worth almost one billion dollars because

the LIGO didn't and basically couldn't discover any new fundamental physics.

The LIGO detected something that is absolutely unavoidable given the general theory of relativity – even at the level at which the theory was almost perfectly understood (by the competent theorists – I don't mean by the general public). So LIGO gave us the ability to "hear" particular astrophysical events – black hole mergers and neutron star mergers so far – which means that it is giving us some new data about astrophysics and perhaps "cosmology close to astrophysics". But it is not producing new data about fundamental physics – and the chance that LIGO could have done so was virtually zero.

In that sense, it dramatically differs from the LHC (or the next colliders) that was (or will be) probing so far untested energy regime of particle physics. Every physicist understands that her suggestion that the colliders are worse than LIGO is absolutely irrational. Here is a CERN response:

Right. In her stupidity that she has enthusiastically exposed in The New York Times, she basically explicitly wrote that LIGO was nice because there was a firm prediction, the gravitational waves, and LIGO got it. On the other hand, the LHC was bad because it discovered the firmly predicted Higgs boson.

What she writes doesn't make any sense. It's nice to confirm firm predictions but if we are really certain about a prediction, then the experiment is pointless. In the case of the LHC and the Higgs boson, we got more information about fundamental physics than in the case of LIGO and gravitational waves: We have learned that the Higgs mass was about \(125\GeV\). The mass was previously unknown. We haven't learned any parameter of fundamental physics from LIGO.

Maybe her obsession with "firm predictions confirmed by experiments" is enough at school, where schoolkids learn lots of things that had been known for a very long time and where schoolgirls are more likely to be praised by their teacher for being "right" and obedient. But the scientific research is something else than the elementary school and the repetition and confirmation of scientific findings that have been known for a long time isn't enough in research!

After numerous additional boring paragraphs full of arrogance, stupidity, and irrelevant technicalities, she wraps up with the final paragraph which starts as follows:

Of course, particle physicists do have a large number of predictions for new particles within the reach of the next larger collider, but these are really fabricated for no other purpose than to rule them out. You cannot trust them. [...]

The only problem with this dumb attack against particle physicists or their work is that it logically cannot influence the benefits of a new collider. The reason is that the scientific benefits of a new collider don't depend on the trustworthiness of the predictions at all.

In fact, the very purpose of the experiment – and basically any experiment in science – is to empirically evaluate the validity of all relevant predictions. The fundamental point about science that this lady still completely misunderstands is that

experiments are not being built in order to confirm firm and guaranteed predictions, to show how trustworthy theorists or their celebrated theories are. Instead, experiments are being built to give us previously unknown or uncertain information and decide which expectations were true and which were not.

The incomplete trustworthiness of predictions not only isn't "fatal" for a meaningful experiment. It is a necessary condition for a meaningful experiment!

Because the \(100\TeV\) collider is going to tell the physicists what happens in that new energy range, whatever it is, we may even say that the scientific benefits of the collider are completely time-independent. So as far as the benefits go, the word "currently" in her title (the collider isn't a good investment) is completely irrational because the benefits for the mankind of probing that energy regime won't change if we delay the experiment by a century (well, unless all people will really turn into stupid apes, in which case the perceived benefits may drop). However, the benefits of a \(100\TeV\) collider built in 2150 AD will be zero for the currently living physicists because at that time, they will be dead. We may include this preference for an earlier collider to a discount rate. It's competing against the dropping expenses. If the expenses drop less quickly than the discount rate, it means that we should build as soon as possible! The previous sentence is an example of an actual rational argument affecting the cost-and-benefit analysis, something that Hossenfelder pretends to do but she never does.

I really find it amazing that an adult woman who has pretended to be a scientist for very many years simply doesn't get this elementary universal point about all of science – that experiments are only meaningful if and because they reduce ignorance or uncertainty.

The very last sentences say:

[...] You cannot trust them. When they tell you that a next larger collider may see supersymmetry or extra dimensions or dark matter, keep in mind they told you the same thing 20 years ago.

And that's very correct that particle physicists are making qualitatively identical statements about supersymmetry as they did 20 years ago – because nothing qualitative has changed about our knowledge about the supersymmetry in the real world around us since that time! There are good reasons to think that supersymmetry exists in Nature – and almost certainty that the superpartners don't have masses in the range of energies that have already been measured.

So indeed, instead, what should raise red flags would be if the physicists were saying something completely and qualitatively different than 20 years ago because that qualitative change would be indefensible!

The broad situation of particle physics hasn't changed – and there are certain truly universal principles about high energy physics that haven't changed in the recent 80 years and that won't change in the next 80 years, either. In particular, a more advanced civilization is capable of building ever stronger colliders that are capable of seeing increasingly massive new particles, resolve ever shorter distances, and most of the general hypotheses that have been neither proven nor falsified yet remain in the state of uncertainty. The fewer new discoveries are made each decade (the Higgs boson was discovered less than 7 years ago, just to be sure), the less quickly the wisdom in physics – and the physicists' commentaries – are changing.

It's a sad testimony to our politically correct epoch that a person who is incapable of understanding these "almost tautologies" is allowed to share her delusions in the New York Times and similar "publications".

P.S.: I realized I forgot to discuss her comment about "alternatives" like the precise electron/muon magnetic moment measurements etc.

Those are indeed cheaper and great but they don't replace the high-energy frontier. They are complementary. An obvious limitation of an anomaly in the magnetic moment that may be found (and that was already found, in the muon case) is that there is no way to attribute the discrepancy to a physical effect. It's just a number – either right or wrong number – but it can't tell us any interesting details about the causes.

More generally, she and others sometimes say "it's right to divide the FCC money to hundreds of [unnamed] experiments". To spread billions of dollars to unnamed experiments means not to care where the money goes – it's a recipe to waste the money. At the end, I think that some people's tendency to "redistribute" or "decentralize" the money is just another example of their Marxist egalitarianism.

Egalitarianism of the communist type is decimating for the economies – and its analogy may be equally devastating for science. Hundreds of such small experiments could be guaranteed to be worthless and their "principal investigators" could easily hide rubbish and unoriginal repetitiveness behind the shortage of scrutiny – because when the money is spread to lots of places, the scrutiny of each goes down considerably.

Small experiments may do interesting things but there's a rather good reason to think that unless there are some overlooked light axions or something weakly coupled in the available energy range, we may be nearly certain that none of these cheap experiments may find anything really and qualitatively new because, if I oversimplify just a little bit, we simply do know all the physics beneath \(1\TeV\). Those are good reasons to think that the money for smaller experiments is much likely to be wasted than the money for an experiment that actually pushes the energy frontier further.

Competent physicists in these fields have simply thought about the question and they can explain why they consider the investment into a higher-energy collider to be a better investment than the investment to the known named alternatives. You can be pretty sure that it's better than unnamed random projects that someone proposes (and that haven't been scrutinized at all), too.